JPH06232131A - Wafer heating device and bump forming device - Google Patents

Abstract

PURPOSE:To make it possible to form ball bumps having little defective on electrodes on each element formed in a wafer by a method wherein a bump forming device is provided with a means, which positions relatively and drives a heating block for heating partially the wafer and a table. CONSTITUTION:When a wafer 3 is fed on a wafer holding stage (a table driving means) 5, a wafer tray 4 is sucked and held on the upper surface of a (theta) table 10. The stage 5 is rotationally positioned in such a way that the table 10 is driven by a driving means 9 and one side of each element 3a is positioned in parallel to an X direction. Then, a heating block 18 is heated to a prescribed temperature and is lagged and at the same time, the block 18 is made to ascend and the upper surface of the block 18 is made to make contact to the lower surface of the table 10. After that, an X table 6 is intermittently actuated by the amount, which corresponds to one element, of the movement of its pitch and the wafer 3 is fed while being driven in the X direction relatively to the block 18. Thereby, as the block 18 is intermittently moved in the direction shown by the arrow formed of dotted lines to the wafer 3, the element 3a shown by the A out of the three elements 3a shown by A, B and C is heated between the movement of the pitch of the table 6 and reaches a proper temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer heating device for heating a wafer and a bump forming device for forming ball bumps on electrodes of a heated wafer.

[0002]

2. Description of the Related Art There are various methods for forming bumps on electrodes of elements formed on a wafer, and one of them is a ball bump forming method.

In this method, for example, a gold wire is inserted through a needle-shaped capillary, and the tip of this wire is melted by electric discharge from an electric torch to form a ball. Then, this ball is pressed against the electrode of the element of the wafer heated to the temperature to bond (bond), and then the wire is cut to form a bump (ball bump) on the electrode. . The wafer on which the ball bumps are formed is then sent to a dicing process and divided into individual elements.

[0004]

By the way, more than 200 elements are formed in the wafer. Therefore, the number of bonding points (the number of electrodes) of the entire wafer reaches 40,000, and therefore, the bonding time per electrode (ball
Even if the formation time of a bump is 0.2 seconds, it may take 2 hours or more for one wafer as a whole.

Since the heating stage is heated to 100 to 250 ° C., it is left at a high temperature for a long time at the place where the ball bump is already formed, and the joint boundary surface, for example, the gold ball and the Al electrode. The intermetallic compound is thickly formed by the diffusion at the joint boundary surface with. Since this intermetallic compound is fragile, there is a problem that the bonding strength is lowered and at the same time Al diffuses into gold and voids are generated at the bonding boundary surface, resulting in a defect.

The present invention has been made in view of the above circumstances, and provides a wafer heating apparatus and a bump forming apparatus capable of forming ball bumps with few defects on the electrodes of each element formed on a wafer. It is intended to be provided.

[0007]

The first means of the present invention is a table for holding a wafer on one surface and a movable surface for the other surface of the table relative to the table. And a driving means for driving the wafer and the heating block to position relative to each other.

A second means is a bump forming apparatus for forming a ball bump on each electrode of a plurality of elements formed on a wafer, and a table for holding the wafer on the upper surface,
A heating block which is arranged on the lower surface side of the table so as to be movable relative to the table and partially heats the wafer, and a positioning drive for the table and the heating block relative to each other. And a ball bump forming means for forming a ball bump on each electrode of the element corresponding to the heating block.

[0009]

According to the first means, only the necessary portion of the wafer can be partially heated. According to the second means, ball bumps can be sequentially formed on the electrodes of the elements located in the heated portion of the wafer.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1A, reference numeral 1 is a base of the bump forming apparatus 2 of the present invention. A wafer holding stage 5 (driving means of the present invention) for holding a wafer tray 4 (holding plate) to which the wafer 3 is attached is provided on the upper surface of the base 1.

The wafer holding stage 5 is provided on the base 1
X table 6 attached to the upper surface of the Y table, a Y table 7 attached to the upper surface of the X table 6 so as to be movable in the X direction, and a Y direction movable to the upper surface of the Y table 7. A support pillar 8 standing upright, a θ drive means 9 attached to one side surface of an upper end portion of the support pillar 8, and an X drive means 9 attached to the θ drive means 9.
Theta table 1 rotatably held in the Y direction in the Y plane
0 (table of this invention).

The upper surface of the θ table 10 is formed horizontal and flat, and a plurality of suction holes 11 are opened in the upper surface of the θ table 10. This suction hole 11
Merge with each other inside the θ table 10 and
It is connected to a suction tube 12 attached to the side surface of the table 10. The suction tube 12 is connected to a vacuum device (not shown). That is, this θ table 10
The wafer tray 4 (holding plate) can be sucked and held on the upper surface by operating the vacuum device.

Further, heating means 14 is provided on the upper surface of the base 1 facing the lower surface of the θ table 10. The heating means 14 has a Z drive cylinder 15 mounted on the base 1 with its axis line vertical, and a holding table 16 mounted substantially horizontally on the upper surface of a drive shaft 15a of the Z drive cylinder 15. A heating block 18 is provided on the upper surface of the holding table 16 via an elastic body 17.

The heating block 18 is mounted so that the upper surface (heating surface) thereof is substantially horizontal, and the shape of the heating surface of the heating block 18 is the X direction as shown by the dotted line in FIG. 1 (b). Are formed in a rectangular shape capable of heating the three elements 3a ... further,
A power source (not shown) for connecting the heating block 18 to the heating block 18 is connected to the heating block 18.

On the other hand, the heating block 18 shown in FIG.
A capillary 20 as a ball bump forming means held by a bonding arm (not shown) is arranged above the element 3a indicated by A in FIG.

A wire 21 made of gold, copper, aluminum or the like for forming bumps is inserted through the capillary 20. At the tip of the wire 21, a ball 21a to be a ball bump later is formed by an electric torch (not shown) when the ball bump is formed. Next, the operation of the bump forming apparatus 2 of the present invention will be described.

The wafer 3 is attached to the wafer tray 4 (holding plate). The wafer 1 is formed by forming ball bumps on each electrode by the bump forming apparatus 2 and then dicing into a lattice shape shown in FIG. 1 (b) to divide each element 3a. A wafer tray 4 (holding plate) shown in FIG. 1 holds a wafer in a state before being diced, and is supplied to the upper surface of the θ table 10 of the wafer holding stage 5 by a wafer tray transfer means (not shown). To be done.

The wafer 3 is placed on the wafer holding stage 5.
If the (wafer tray 4) is supplied, the vacuum device operates and the wafer tray 4 is placed on the upper surface of the θ table 10.
(Holding plate) is suction-held. The wafer holding stage 5
Activates the θ drive means 9 to move the θ table 10
Is driven in the θ direction, so that one side of the element 3a is rotationally positioned so as to be parallel to the X direction.

Then, the heating means 14 is operated to heat and keep the heating block 18 at a predetermined temperature.
By operating the Z drive cylinder 15 and driving the heating block 18 upward, the upper surface of the heating block 18 is elastically brought into contact with the lower surface of the θ table 10.

At this time, the heating block 18 can simultaneously heat the three elements 3a (shown by A to C in FIG. 1B) of the wafer 3 held on the upper surface of the θ table 10. Is positioned in the state.

Next, the wafer holding stage 5 intermittently operates the X table 6 by an amount corresponding to one element, and moves the wafer 3 relative to the heating block 18 by X.
Drive in the direction.

As a result, the heating block 18 is intermittently moved relative to the wafer 3 in the direction shown by the dotted arrow in FIG. 1B, and the element 3a heated by the heating block 18 is moved by the arrow. It will be shifted one by one in the direction opposite to the direction indicated by.

Therefore, of the three elements 3a shown by A to B in the figure, the element 3a of A located on the rear side in the traveling direction of the heating block 18 is heated for a time corresponding to the movement of 3 pitches. It is the highest temperature.

Further, the bump forming apparatus 2 controls the temperature of the heating block 18 so that the temperature of the element 3a of A becomes the most suitable temperature for bonding. That is, the elements 3a and 3a indicated by B and C in the figure are in a preheated state.

The capillary 20 is the element 3 of the A portion.
A ball bump is formed on each electrode of a. A gold wire, for example, is inserted through the capillary 20. Then, the bump forming apparatus 2 forms a ball 21a at the tip of the gold wire 21 by an electric torch (not shown) by discharging, and the ball 21a is formed by the capillary 20 into each element of the wafer 3. After the wire 21 is pressed and bonded to the electrode 3a, the wire 21 is cut to form a ball bump on the electrode.

A button is placed on all electrodes of the element 3a of A above.
If the bumps are formed, the bump forming device 2
The Y table 7 of the wafer holding stage 5 is operated for one element pitch, and the heating portion of the heating block 18 is shifted by one element. As a result, the element 3 in the portion B shown in FIG.
a becomes the element 3a of A and is heated to a predetermined bonding temperature. Then, the bump forming device 2 operates the capillary 20 to form a ball bump again on the electrode of the element 3a.

As shown in FIG. 2, the heating block 18 is
Since the relative positional relationship between the capillaries and the capillaries 20 does not change, the capillaries 20 always face above the element (indicated by A in the figure) heated to the most suitable temperature for bonding, and the capillaries are placed on the electrodes of the element A. The bumps can be formed.

When the ball bumps are formed on all the elements 3a of the wafer 3, the heating block 18 is moved relative to the wafer 3 (θ table 10) as shown in FIG. Move it.

Here, the chain line in FIG. 3 indicates the drive path when the upper surface of the heating block 18 is in contact with the lower surface of the θ table 10, and the dashed line indicates the Z drive. This is a drive path in a state where the cylinder 10 is operated and the upper surface of the heating block 18 is separated from the lower surface of the θ table 10.

According to this route, the heating block 1
By intermittently positioning and driving 8 for each element, ball bumps can be sequentially formed on all the elements 3 a housed in the wafer 3.

When the ball bumps are formed on all the electrodes of each element 3a formed on the wafer 3, the wafer tray 4 (holding plate) is moved to the wafer holding stage 5 (θ).
It is taken out from the upper surface of the table 10) by a wafer tray taking-out means (not shown). Then, the wafer tray 4 (holding plate) is transferred to a dicing process (not shown), and the wafer 3 is divided into individual elements 3a.

According to this structure, only the element 3a (A) forming the ball bump is heated to the most suitable temperature for bonding, and the element 3a is formed.
Since a is not heated after the ball bump is formed on the Al electrode, an alloy layer develops on the joint surface, and
Rarely diffuses into the above ball bumps

As a result, defects such as voids do not occur in the ball bumps, and it is possible to form high quality ball bumps on the electrodes of each element 3a of the wafer 3. It should be noted that the present invention is not limited to the above-mentioned one embodiment, and can be variously modified without changing the gist of the present invention. For example, in the above embodiment,
Although the wafer holding stage 5 is driven in the XY directions, it may be driven in the heating block 18XY directions.

Further, in the above-mentioned embodiment, the shape of the heating surface (upper surface) of the heating block 18 is such that the three elements 3a can be heated at the same time, but the present invention is not limited to this. It may have a configuration capable of heating four or more or only one. The point is that the element 3a on which the ball bumps are already formed need not be heated more than necessary.

The mechanism for partially heating the wafer 3 is not limited to the one applied to the bump forming apparatus. Other devices can be applied as long as they are devices that require heating of the wafer 3.

[0037]

As described above, according to the first structure of the present invention, a table for holding a wafer on one surface and a table for holding the wafer on the other surface side of the table relative to this table are provided. It is a wafer heating apparatus provided with a heating block which is movably arranged and partially heats the wafer, and a driving unit which relatively drives the table and the heating block to position relative to each other.

The second structure is a bump forming apparatus for forming a ball bump on each electrode of a plurality of elements formed on a wafer, and a table for holding the wafer on the upper surface,
A heating block which is arranged on the lower surface side of the table so as to be movable relative to the table and partially heats the wafer, and a positioning drive for the table and the heating block relative to each other. And a ball bump forming means for forming a ball bump on each electrode of the element corresponding to the heating block.

With such a structure, only a necessary portion of the wafer can be heated, and the ball bump can be formed on the element located at the heated portion. By this, since the element is not heated after the ball bump is formed, it is possible to prevent the alloy layer and the like from developing at the boundary between the bump and the electrode, and to obtain a ball bump of higher quality. There is an effect that can be formed.

[Brief description of drawings]

1A and 1B are a front view and a plan view of an embodiment of the present invention.

2 (a) and 2 (b) are a front view and a plan view showing the same operation.

FIG. 3 is a plan view showing the drive path of the wafer holding stage.

[Explanation of symbols]

2 ... Bump forming device, 3 ... Wafer, 3a ... Element, 5 ... Wafer holding stage (driving means), 10 ... Theta table, 18 ... Heating block, 20 ... Capillary (ball bump) Forming means).

Claims (2)

[Claims] 1. A table for holding a wafer on an upper surface thereof, and a heating block arranged on the lower surface of the table so as to be movable relative to the table and for partially heating the wafer. And a driving means for relatively positioning and driving the table and the heating block. 2. A bump forming apparatus for forming a ball bump on each electrode of a plurality of elements formed on a wafer, wherein a table for holding the wafer on an upper surface and a table for holding the wafer on a lower surface side of the table. A heating block which is arranged so as to be movable relative to the table and which partially heats the wafer; a driving means which relatively drives and positions the table and the heating block; and the heating block. A bump forming apparatus comprising: a ball bump forming means for forming a ball bump on each electrode of a corresponding element.